This is the first application filed for the present invention.
Not applicable.
The invention relates to modular page-wide array (PWA) print heads, and, in particular, to a method and apparatus for precision-mounting and removing page-wide array print heads by unskilled technicians.
Recent developments in ink-jet printing technology have led to the realization of page-wide arrays (PWAs) of ink-jet print heads all oriented in the same direction in a linear array. Each print head is composed of a linear array of evenly-spaced ink-jet nozzles. The print heads in a PWA extend in the direction defined by the width of the print head (horizontally, for the purposes of discussion) across the entire width of the allowable printing area. Thus, the PWA does not need to move horizontally relative to the printing material, in order to provide print coverage across the width of the printing area. Rather the material to be printed is typically mounted on a web which passes vertically past the PWA. This permits printing at speeds heretofore impossible to achieve with ordinary ink-jet printers.
Additionally, multiple PWAs are organized in a vertical array, in which each PWA is offset by a fraction of the horizontal separation between adjacent nozzles within a print head. Thus, the cumulative effect of the vertical array of PWAs permit a print resolution in the horizontal direction which is a multiple of the print resolution of the print head in isolation. The print resolution in the vertical direction is defined by the speed at which the web passes relative to the vertical array of PWAs, together with the space between the nozzles of the PWA array and the web itself.
In addition to providing a greater horizontal print resolution, arrangements of multiple PWAs may be positioned in close proximity to produce a compact printing apparatus. The nature of the constituent PWAs define the function of the resulting apparatus, such as providing 4- or higher colour separation or ultra-high resolution monochrome printing.
While PWAs provide significant advantages in the printing art, the large number of print heads causes concomitant maintenance problems. Ink-jet cartridges, by their nature, require frequent, regular and relatively complex service. The large number and close proximity of the print heads within PWAs and the close proximity of PWAs within a printing apparatus, as well as the typically tight spacing between print head nozzles and the web exacerbates the problem. Typically, print heads are required to be removed in order to be serviced and or replaced. The nature of the PWA requires that the component print heads be precisely aligned within a PWA and with respect to other PWAs. While PWAs may be inserted and removed as a single replaceable unit, the installation and removal of PWAs has nevertheless typically required the use of highly skilled technicians and the process of removal and installation has been time-intensive, leading to considerable expense in the form of labour costs and down time of the printing apparatus.
What is therefore required is an apparatus for supporting multiple PWAs in a printing apparatus, so that the PWAs can be quickly removed and replaced by non-skilled technicians, while maintaining the precise alignment between PWAs in the printing apparatus.
Therefore an object of the invention is to provide a structure for maintaining a PWA in a precise orientation within a printing apparatus that permits rapid insertion and removal of the PWA by non-skilled personnel.
In accordance with the present invention, there is provided a bay for supporting a page-wide array (PWA) of print heads. The bay may be configured in a vertical array to permit multiple PWAs to be simultaneously supported in a printing apparatus. The bay includes a support structure having supporting surfaces for maintaining the proper vertical orientation of the PWA as it is inserted into, maintained within and removed from the bay. The spacing between the supporting surfaces of the bay is such that the PWA is sufficiently constrained from vertical movement, without unduly inhibiting the insertion and removal of the PWA. The supporting surfaces do not obstruct the nozzles of the PWA print head from projecting ink horizontally from a vertical face of the PWA.
The bay is fixed with reference to a wall structure and an adjustable protrusion permits horizontal precise positioning of the PWA within the bay with respect to the wall, which together provide for alignment of the PWA print head within the bay. The protrusion consists of a bolt having an exterior thread that engages an internal threaded bore in the wall to permit adjustment in the horizontal direction. The pitch of the exterior thread is sufficiently fine to permit precision alignment of the PWA relative to the wall. An internal bore in the bolt permits rotation of the bolt to the desired depth using an Allen key. The protrusion is locked into place relative to the wall by a nut that engages the exterior thread of the bolt within the bay.
The bay also provides a convenient locking mechanism disposed at an opening at an end distal from the wall. The PWA is inserted and removed through the opening when the locking mechanism is in an open position. The locking mechanism may be moved into a closed position where it applies a persistent force on a PWA situated in the bay, to urge the PWA print head into contact with the print head locater. Where the printing apparatus features a vertical array of bays, the locking mechanism of each bay is linked, so that the bays may be opened or closed by a single operation.
Also according to the objects of the invention, a printing apparatus with multiple page-wide array (PWA) print heads is provided. The printing apparatus includes a system for feeding a print medium at a predetermined rate across a printing area to a print output, a plurality of PWA print heads for imparting ink onto the print medium in accordance with a bit map received by a signal processing means of the printing apparatus, and a bay as described above for each of the PWAs.
A method for replacing a page-wide array (PWA) in a printing apparatus is also provided in accordance with an aspect of the invention. The method involves opening a locking mechanism that obstructs the opening to the bay that encloses the PWA; removing the PWA from the bay through the opening; inserting a replacement PWA print head into the bay through the opening; and closing the locking mechanism so that the locking mechanism urges the PWA print head into contact with a print head locater in a fixed position with reference to a wall to which the bay is attached, wherein the supporting structure of the bay constrains the vertical positioning of the PWA and the locking mechanism and the protrusion constrain the horizontal positioning of the PWA.